Widgets: Enable oEmbed support for Video widget

With #34115 now resolved, we can now support oEmbeds in the video widget instead of limiting the widget to just playing what is supported by MediaElement.js. See previously #40935 where the video widget was explicitly limited to support YouTube and Vimeo since these were the only hosted video providers that MediaElement.js supported directly without needing to resort to oEmbed.

Note also that oEmbeds are now supported in the rich Text widget as well, so there may need to be some changes done for that widget in particular to apply the same inject_video_max_width_style logic that the Video widget is applying now to the Video shortcode output.